Cognitive Radio Communication and Networking: Principles and Practice

Chapter 2

Spectrum Sensing: Basic Techniques

2.1 Challenges

Spectrum sensing in a cognitive radio is practically challenging, as shown in Table 2.2 [36, 37].

2.2 Energy Detection: No Prior Information about Deterministic or Stochastic Signal

Energy detection is the simplest spectrum sensing technique. It is a blind technique in that no prior information about the signal is required. It simply treats the primary signal as noise and decides on the presence or absence of the primary signal based on the energy of the observed signal. It does not involve complicated signal processing and has low complexity. In practice, energy detection is especially suitable for wideband spectrum sensing. The simultaneous sensing of multiple subbands can be realized by scanning the received wideband signal.

Two stages of sensing are desirable. The first stage uses the simplest energy detection. The second stage uses advanced techniques.

Table 2.1 Receiver parameters for 802.22 WRAN

Table 2.2 Challenges for spectrum sensing

Practical challenges	Consequences	Comments
Very strict sensing requirements	See Table 2.1	To avoid “hidden node” problem
Unknown propagation channel and nonsynchronization	Make coherent detection unreliable	To relieve the primary user from the burden
Noise/interference uncertainty	Very difficult to estimate their power	Change with time and location

We follow [38] and [39–42] ...